Effect of annealing temperature on structural and magnetic properties of nano-cobalt ferrite

Abstract

In this paper, the induced effect of annealing temperature on structural and magnetic response of nano-crystalline cobalt ferrite prepared via sol–gel auto-combustion method using metal nitrates and citric acid has been reported. The X-ray diffraction pattern confirms the formation of cubic spinel structure of the annealed nano-crystalline cobalt ferrite belonging to the Fd3m space group. From the X-ray diffraction pattern it is observed that lattice parameter and crystallite size increase from 8.3801 to 8.3937 Å and 26.38 to 56.53 nm, respectively, with the increasing annealing temperature up to 1000 °C. The A_1g and E_g modes in the Raman spectra and the vibrational frequencies of metal–oxygen (M–O) ions in the FTIR spectra also confirm the existence of the cubic spinel structure of nano-crystalline cobalt ferrites. The shift in the peak position of the Raman spectra shows the migration of Fe³⁺/Co²⁺ ions between the tetrahedral and octahedral sites. The magnetization response shows that saturation magnetization increases from 53.17 emu/g (2.13 μ_B/f.u.) to 77.94 emu/g (3.27 μ_B/f.u.), while coercivity lies between 1838.32 and 679.15 Oe with the increasing annealing temperature up to 1000 °C.